US20120251321A1

US20120251321A1 - Impeller and centrifugal fan

Info

Publication number: US20120251321A1
Application number: US13/423,912
Authority: US
Inventors: Manabu FUCHIBE
Original assignee: Minebea Motor Manufacturing Corp
Current assignee: Minebea Co Ltd
Priority date: 2011-03-31
Filing date: 2012-03-19
Publication date: 2012-10-04
Also published as: DE102012102626A1; JP2012215099A

Abstract

Herein disclosed are an impeller and a centrifugal fan having the same. The impeller includes a cup-shaped metallic hub having a cylindrical portion. The hub includes a flange extending outwardly from an edge of the cup, a plurality of resin vanes disposed above an outer portion of the flange and coaxially with the cylindrical portion, and an annular part made of resin supporting the plurality of resin vanes thereon and holding the outer portion of the flange embedded therein.

Description

BACKGROUND OF THE INVENTION

1. Field of the Invention
The present invention relates to an impeller used as a rotating part of a fluid apparatus such as a fan motor.
2. Description of the Related Art (or Background Art)
Conventionally, a number of configurations of a fan motor using an impeller have been provided in accordance with various applicable situations. For example, the centrifugal fan disclosed in JP-A-2007-120378 is an outer rotor type centrifugal fan, in which an impeller adapted to rotate and generate air flow is provided with a plurality of main vanes and a plurality of auxiliary vanes integrally formed with the inner circumference of the impeller. A cup portion is disposed at the rotation center of the impeller, and the auxiliary vanes are connected to the outer surface of the cup portion. The outer side of the cup portion serves as an outer cup portion formed of a resin in an approximately cylindrical shape having a bottom and integrally molded with the entire impeller. A metallic yoke member is press-fitted and fixed to the outer cup portion for a single purpose of converging magnetic flux.
On the other hand, the blower impeller disclosed in JP-A-2005-54692 is provided with a plurality of airfoil vanes surrounding a cylindrical hub. The hub and airfoil vanes are integrally molded of a resin, and no metallic yoke is disposed at the center of the hub.
Since a fan motor or the like using an impeller has versatile applications, in some cases a heat resistance to a wide temperature range from below zero to 100 degrees Celsius or more (more specifically, for example, from −40 to 125 degrees Celsius) is required. In the above example of JP-A-2007-120378, the outer cup portion is made of a resin, and the yoke press-fitted thereinto is made of a metal. Since these two materials are different in thermal expansion coefficients from each other, a drawback arises that the outer cup portion may crack due to heat shock.
In the above example of JP-A-2005-54692, the entire impeller is made of a resin mixed with thermoplastic elastomer. However, when exposed to a wide range of temperature such as the above mentioned, there has also been a drawback that heat shock crack could not be prevented.
In view of the foregoing drawbacks, it is an object of the present invention to provide an impeller which can meet the strict requirements of environmental resistance such as heat resistance and shock resistance, while achieving cost reduction and weight saving to the degree equal to or greater than those of the conventional configurations.

SUMMARY OF THE INVENTION

The impeller according to the present invention is configured to comprise a cup-shaped metallic hub having a cylindrical portion, the hub comprising a flange extending outwardly from an edge of the cup, a plurality of resin vanes disposed above an outer portion of the flange and coaxially with the cylindrical portion, and an annular part made of resin supporting the plurality of resin vanes thereon and holding the outer portion of the flange embedded therein.
The impeller is preferably configured such that the plurality of resin vanes and the annular part include an elastomer.
The impeller is preferably configured such that at least the outer portion of the flange embedded in the annular part has a form which is not perpendicular to the rotation axis of the cylindrical portion.
The impeller is preferably configured such that the plurality of resin vanes and the annular part include a glass fiber.
It is preferable to provide a centrifugal fan configured to comprise the impeller and a motor rotating the impeller.
According to the above configuration, the entire hub is made of metal, and the resin-metal joint area is limited to the flange portion only. Thus, it becomes possible to reduce the area subjected to the effect caused by the difference in thermal expansion coefficients and to suppress crack generation due to heat shock even in a service condition of a wide temperature range. Furthermore, since no resin is used in the hub, it becomes possible to reduce weight of the hub in comparison with the prior art, which is also advantageous with respect to reduction of raw material cost.
Moreover, by mixing an elastomer into the resin material of vanes and annular part, it becomes possible to improve elasticity of the resin material and to increase the effect of suppressing crack generation due to heat shock.
Also, by mixing a glass fiber into the resin material of vanes and annular part, it becomes possible to improve shock resistance as well as the effect of suppressing crack generation due to heat shock.
According to the present invention, it becomes possible to provide an impeller which can suppress crack generation due to heat shock even under a high temperature environment while enhancing shock resistance. Also, it becomes possible to provide an impeller which is advantageous to the weight reduction of the hub portion as well as cost reduction in terms of raw material.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a perspective view of an impeller according to one embodiment of the present invention;

FIG. 2 is a front view of the impeller shown in FIG. 1;

FIG. 3 is a cross-section view along the line A-A of the impeller shown in FIG. 2;

FIG. 4 is a partial cross-section view showing another shape of a flange of the impeller according to one embodiment of the present invention;

FIG. 5 is a top view of a blower as one embodiment of a centrifugal fan that employs the impeller according to the present invention; and

FIG. 6 is a cross-section view along the line B-B shown in FIG. 5.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

In the following, a description of a preferred embodiment of an impeller according to the present invention will be given. FIG. 1 is a perspective view of an impeller according to the present invention. FIG. 2 is a front view of the impeller shown in FIG. 1. FIG. 3 is a cross-section view along the line A-A of the impeller shown in FIG. 2.
As shown in FIGS. 1 and 2, an impeller 10 of the present embodiment is constituted of resin vanes 11, a cup-shaped metallic hub 13, an upper annular part 15, and a lower annular part 17. As shown in FIG. 3, the metallic hub 13 is shaped like a cup having a cylindrical portion 14. A flange 18 extends outwardly the cylindrical portion 14 from an edge 16 of the cup shape. A shaft 21 is fixed by means of a boss 22 to a rotation axis center of the hub 13.
The resin vanes 11 are disposed above an outer portion of the flange 18 and coaxially arranged with respect to the shaft 21 of the cylindrical portion 14. The vanes 11 are disposed circumferentially equidistant between the upper annular part 15 and the lower annular part 17 to form a multi-blade structure. The vanes 11, the upper annular part 15, and the lower annular part 17 are integrally molded by resin.
The lower annular part 17 is molded such that the outer circumference of the flange 18 is embedded in the lower annular part 17 at the time of integral molding. This makes it possible for the flange 18 and the lower annular part 17 to rotate integrally, and thus, the impeller 10 is formed such that the resin vanes 11, the cup-shaped metallic hub 13, the upper annular part 15, and the lower annular part 17 rotate integrally.
The resin-metal joint portion is formed only at the outer portion of the metallic flange 18. Since no resin is used in the cup portion constituting the major part of the hub 13, the portion which can suffer a crack is eliminated. Also, the joint portion, which is exposed to the effect of difference in thermal expansion coefficients, is limited to a small area corresponding only to the outer periphery of the flange 18. Therefore, the heat shock effect is minimized even in a high temperature environment. Furthermore, since a resin portion is eliminated from the cup portion, it serves advantageously to reduce weight and raw material. Moreover, since the hub 13 is made of a metal, it can still serve as a yoke.
As shown in FIG. 3, inside of the lower annular part 17, at least a part of the flange 18 is bent upwardly toward the upper annular part 15 from a plane perpendicular to the shaft 21 which is the rotation axis of the cylindrical portion 14. This means that the angle formed by at least a part of the outer portion of the flange 18 embedded in the lower annular part 17 and the direction of the rotation axis is smaller than 90 degrees (an acute angle). Such a structure makes it possible to increase the binding force between the flange 18 and the lower annular part 17 which contributes to reduce the joint area, and to provide a stable rotation even in a high temperature environment.
The resin material to be used for the impeller 10 may be mixed with an elastomer. As a combined effect of mixing the elastomer into the resin material and employing the configuration of the impeller 10 according to the present invention, generation of crack in the resin material used for the impeller 10 is further suppressed.
A glass fiber may be mixed into the resin material to be used for the impeller 10. The amount of the glass fiber should be in a range of 15 to 40% (weight percent), most preferably approximately 30%. As a result of mixing the elastomer into the resin material and employing the configuration of the impeller 10 according to the present invention, shock resistance of the impeller 10 is increased. Here, the shock resistance means the resistance to shock (mechanical force) imparted from outside. Furthermore, by mixing the elastomer as well as the glass fiber into the resin material to be used for the impeller 10, crack generation in the resin material used for the impeller 10 is further suppressed, in addition to improving the shock resistance of the impeller 10.
FIG. 4 is a partial cross-section view showing another shape of the flange of the impeller according to the present invention. As shown in FIG. 4, the cross-sectional shape of a flange 58 extending from an edge 56 of a cylindrical portion 54 is waved. Such a wavelike shape can further improve the binding force without increasing the range of the joint area of the flange 58 and the lower annular part 17 (in a left-right direction in FIG. 4). Besides this configuration, the binding force between the flange and the lower annular part 17 can be improved by making the shape of the flange 18 in the hub so that the angle formed by the flange 18 and the rotation axis is not perpendicular, i.e. it is acute, at least inside the lower annular part 17.
FIG. 5 is a top view of a blower as one embodiment of a centrifugal fan that employs the impeller according to the present invention. FIG. 6 is a cross-section view along the line B-B shown in FIG. 5. An impeller 40 is arranged inside a case 33 of a blower 30. The case 33 is formed with an inlet opening 38 a on a top surface of the blower 30 and an outlet opening 38 b on a side surface of the blower 30. A stator assembly 34 is fixed on an outer circumference of a cylindrical wall 36 protruding from a base 35 arranged on a bottom surface of the case 33. The stator assembly 34 includes a core 34 a and a coil 34 b. A bearing 37 is fixed on an inner circumference of the cylindrical wall 36. The bearing 37 rotatably supports a shaft 31. The shaft 31 holds a cup-shaped hub 43 via a boss 32. A magnet 39 is fixed at a cylindrical portion of the hub 43.
Since the bottom of the hub 43 connected with the boss 32 has an outer diameter smaller than that of the cylindrical portion, the portion between the cylindrical portion and the bottom is shaped like a circular truncated cone. Furthermore, the hub 43 is lower in height than the vanes. Such a structure facilitates smooth inflow of air from the inlet 38 a.
The configuration of vanes 41 and a flange 48 is similar to that of the vanes 11 and the flange 18 shown in FIGS. 1 to 3. This means that the flange 48 extends from an edge of the cylindrical portion of the metallic hub 43. An outer portion of the flange 48 is molded at the lower position of the vanes 41 so as to be embedded in resin at the time of integral molding of the impeller 40. In this manner, the flange 48 and the vanes 41 become integral, and thus, the impeller 40 is formed such that the resin vanes 41 and the cup-shaped metallic hub 43 rotate integrally.
The magnet 39 attached inside the metallic hub 43 is combined with the stator assembly 34 to form an electric motor, which rotates the impeller 40 when voltage is applied to the exciting circuit (not shown) on a printed circuit board in the stator assembly 34. By way of such rotation of the impeller 40, air around the blower 30 is received from the inlet 38 a and discharged from the outlet 38 b.
At this time, even if the temperature around the blower 30 is high, for example, at 100 degrees Celsius, since the joint area of the flange 48 and the vanes 41 is small and the elastomer as well as glass fiber is mixed to the resin, the impeller 40 becomes less susceptible to heat shock even in such a high temperature environment.
Further, the flange 48 is provided with a plurality of slits 49 in a circumferential direction at the inner circumferential portion between the vanes 41 and the hub 43 maintaining the rotational balance. The slits 49 serve to improve the air flow inside the blower 30 and also to exhaust heat from the stator assembly 34.
According to the blower 30 thus configured, it is possible to provide a blower which can meet the heat resistance requirement ranging, for example, from −40 to 125 degrees Celsius and exhibit stable performance.
Here, the metallic hub according to the present invention is usually made of steel. However, any material may be employed so long as it can converge magnetic flux without loss and exhibit enough strength as a rotating member. Also, any vane shape and any kind of the impeller may be employed so long as it is configured to allow a metallic yoke to be incorporated therein.
As described above, according to the above embodiment of the present invention, since the entire hub portion of the impeller is metallic and the joint portion of resin and metal is limited to the outer portion of the flange extending from the hub, the area subjected to the effect of difference in thermal expansion coefficients is minimized, and the crack generation due to heat shock can be suppressed even when exposed to a wide variation in temperature. Furthermore, since no resin part is used in the hub, it is possible to reduce weight in comparison to the prior art, which is also advantageous with respect to reduction of raw material cost.
It should be noted that the present invention is not limited to the embodiment described above, and modifications and improvements thereto within the scope in which an object of the present invention can be realized, are included in the present invention.

Claims

1. An impeller comprising:

a cup-shaped metallic hub having a cylindrical portion, the hub comprising a flange extending outwardly from an edge of the cup;

a plurality of resin vanes disposed above an outer portion of the flange and coaxially with the cylindrical portion; and

an annular part made of resin supporting the plurality of resin vanes thereon and holding the outer portion of the flange embedded therein.

2. The impeller according to claim 1, wherein the plurality of resin vanes and the annular part include an elastomer.

3. The impeller according to claim 1, wherein at least a part of the outer portion of the flange embedded in the annular part has a form which is not perpendicular to the rotation axis of the cylindrical portion.

4. The impeller according to claim 1, wherein at least a part of the outer portion of the flange embedded in the annular part is bent upwardly to form an acute angle with the rotation axis of the cylindrical portion.

5. The impeller according to claim 1, wherein at least a part of the outer portion of the flange embedded in the annular part has a waved form.

6. The impeller according to claim 1, wherein the plurality of resin vanes and the annular part include a glass fiber.

7. A centrifugal fan comprising the impeller according to claim 1 and a motor rotating the impeller.